NEW YORK (CBSNewYork) — Mail something through the post office that didn’t make it on time for Christmas?

As WCBS 880’s Ginny Kosola reported, it’s possible you didn’t understand the way priority mail is delivered.

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If you used the United States Postal Service’s priority mail thinking it would be delivered in two days, you should know, the post office says the service is not guaranteed to arrive on a particular day.

For that, you need to send things priority express mail, Kosola reported.

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The postal service says it did have a terrific season, delivering approximately 560 million packages between Thanksgiving and Christmas.

The agency predicted an increase of 12 percent in package volume, but instead saw a 26 percent increase.

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